What is the difference between t and d in the run command in docker?

In docker, the run command is used to create a new container and run a command. Setting the parameter "-t" can reassign a pseudo input terminal to the container, and setting the parameter "-d" will Run the container in the background and return the container ID.

The operating environment of this tutorial: linux7.3 system, docker-1.13.1 version, Dell G3 computer.

What is the difference between t and d in the run command in docker

docker run: Create a new container and run a command

Syntax

docker run [OPTIONS] IMAGE [COMMAND] [ARG...]

OPTIONS description:

• -a stdin: Specifies the standard input and output content type, optional STDIN/STDOUT/STDERR;

• -d : Run the container in the background and return the container ID;

• -i: Run the container in interactive mode, usually used with -t;

• -P: Random port mapping, the container's internal port is randomly mapped to the host's port

• -p: Specifies the port mapping, the format is: host (host) port:container port

• -t: Reassign a pseudo input terminal to the container, usually used together with -i;

• --name="nginx-lb": Specify a name for the container;

• --dns 8.8.8.8: Specify the DNS server used by the container, which defaults to the same as the host;

• -- dns-search example.com: Specifies the container DNS search domain name, which is consistent with the host by default;

• -h "mars": Specifies the hostname of the container;

• -e username="ritchie": Set environment variables;

• --env-file=[]: Read environment variables from the specified file;

• --cpuset="0-2" or --cpuset="0,1,2": Bind the container to the specified CPU to run;

• -m :Set the maximum memory used by the container;

• --net="bridge": Specify the network connection type of the container, supporting bridge/host/none/container: four types;

• --link=[]: Add a link to another container;

• --expose=[]: Open a port or a group of ports ;

• --volume, -v: bind a volume

For example: "I want to run a mirror in the background", when I When executing the following command

docker run -d --name server somebody:dockerfile

, check whether the operation is successful through docker ps, but find that it is not running successfully. What is the situation? ? Isn’t it necessary to use the -d parameter to run in the background? In fact, the main reason is that this image may have CMD added at the end, similar to

CMD ["/bin/bash"]

, which means that when you run it in the background, the container created by this image will first execute /bin/bash, which means that when running in the background When running (-d), the shell exits immediately. So unless the command is not running in the foreground, the container will stop immediately

Solution

Provide a pseudo "tty n" for -d through -i or -t

docker run -i -d images:tags
docker run -t -d images:tags
docker run -itd images:tags

Add tail -f /dev/null to the command

By doing this, the container will not stop even if the main command is running in the background because tail will continue running in the foreground.

docker run -d centos tail -f /dev/null

The same is true for the other situation (entering the container). Docker officially recommends the use of -i and -t to make it behave like a shell.

docker run -i -t <images:tags>

Recommended learning: "docker video tutorial"

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